The present invention relates to the field of data tunnelling. Particularly, but not exclusively, the invention relates to the tunnelling of Internet Protocol (IP) data across an Open Systems Interconnection (OSI) based network.
Many conventional Data Communication Networks (DCNs), such as a Synchronous Digital Hierarchy (SDH) network or Synchronous Optical Network (SONET), are based on the open systems interconnection (OSI) reference model. The network elements (NEs) operate, and communicate with one another, using OSI protocols.
In an Internet protocol (IP) network, such as the Internet or an Intranet, the network devices, such as personal computers (PCs), communicate with one another using an alternative set of protocols, such as Transmission Control Protocol/Internet Protocol (TCP/IP) or User Datagram Protocol/Internet Protocol (UDP/IP).
With the increasing popularity of IP devices and IP communication, and given the relatively large infrastructure of existing data networks which are OSI based, it is desirable to enable IP devices to communicate across an OSI network and vice versa.
There is a fundamental problem, however, in that OSI and IP protocols do not interoperate. IP data cannot therefore be sent directly over an OSI network and vice versa.
It is known to address this problem using a technology known as data tunnelling. Data tunnelling is the encapsulation of a first protocol within a second protocol. For example, in IP over OSI data tunnelling, IP data is encapsulated within OSI packets that are suitable for transmission across an OSI network. To implement data tunnelling, each network element (NE) in the OSI network includes a look-up table that correlates OSI addresses and IP addresses (or IP sub-nets). When an NE is to send IP data to an IP device across the OSI network, the NE determines an IP address, or IP subnet, associated with the recipient IP device and refers to the look-up table to determine a corresponding OSI address. The NE then encapsulates the IP data into OSI data packets, incorporating the determined OSI address.
The OSI network element also includes a database, commonly known as a Routing Information Base (RIB), which includes information describing the topography of the network to which the NE is connected, namely, identification of each of the other NEs connected to the network and an indication of their relative positions in the network.
Once the IP data is encapsulated, the NE refers to the RIB to determine how the encapsulated IP data packet should be routed in order to reach said determined OSI address and sends the encapsulated data across the OSI network accordingly.
A problem with this arrangement is that conventional lookup tables are static and need to be manually updated if there are any changes in the OSI network. In general, as long as there is an OSI route between the start point and end point of a data tunnel, then normal OSI routing protocol (ISIS) causes the tunnel to re-route, or reconfigure, to accommodate changes in the OSI network. However, should the start or end points of a tunnel change, then there is a requirement to reconfigure the tunnel manually. For example, if a further NE is added to the network, or one of the existing NEs is removed, then the look-up table of each NE in the network must be updated manually. Conventionally, therefore, the data tunnels created by encapsulation are static and require manual configuration to accommodate certain changes in the network. This is undesirable since manual tunnel configuration is labour intensive and time consuming. Further, any undue delays in reconfiguring the data tunnels to reflect changes in the network can result in loss of data.
Accordingly, a first aspect of the invention provides a network element associated with a first identifier,
complying with a set of one or more first protocols, and with one or more second identifiers, complying with a set of one or more second protocols, the network element being arranged for operation in a network that includes one or more other like network elements,
the network element including a directory of respective first identifiers and respective second identifiers for at least said other like network elements,
the network element being arranged to generate a routing data packet and to cause said routing data packet to be distributed to said other network elements,
wherein said routing data packet includes routing information identifying said first identifier and said one or more second identifiers,
and wherein the network element is arranged to, upon receipt of a routing data packet from another like network element, determine said routing information from said received routing data packet and to update said directory in respect of said other like network element.
Thus, each directory is automatically updated to reflect changes in the network. This arrangement has the effect of creating dynamic data tunnels across the network and significantly reduces the need for manual tunnel configuration in the network.
One aspect of the invention relates particularly to the tunnelling of IP data across an OSI network. An alternative aspect of the invention relates particularly to the tunnelling of OSI data across an IP network.
The invention also provides a network comprising one or more network elements according to the first aspect of the invention. In one embodiment, the network is arranged to support OSI protocols. In an alternative embodiment, the network is arranged to support IP protocols. In a further embodiment, the network comprises a plurality of network areas, at least one of said network areas being arranged to support IP protocols including Integrated IS-IS routing protocol, and at least one of said other network areas being arranged to support OSI protocols including IS-IS routing protocol.
The invention further provides a method of maintaining data tunnels in a network comprising network elements according to the first aspect of the invention.
The invention also provides a computer program and a computer program product arranged for implementing the network element, network and method of the invention in whole or in part. In particular, the invention provides a computer readable medium comprising computer program instructions for causing a network element to perform said method of maintaining data tunnels.
Other aspects of the invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention and with reference to the accompanying drawings.